JPH0116889Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a rice husk incinerator using a fluidized bed incinerator.

Traditionally, rice husks generated in large quantities after rice harvest were incinerated in a simple incinerator with a fire bed at the bottom of a cylindrical combustion chamber, but the incinerator not only had problems with its durability, but also The period was long and there were problems such as secondary pollution from soot and smoke caused by incineration.

In order to solve this problem, the applicant incinerated the incinerator in a fluidized bed incinerator using a sand bed, sent the incinerated ash along with the combustion gas to an exhaust gas cyclone through a heat exchanger, extracted the incinerated ash, and collected the incinerator using the heat exchanger. He developed a rice husk incineration device that uses the heat from the rice husks as a heat source for a dryer (Utility Application No. 112473, 1983).

To explain this outline with reference to FIG. 1, a fluidized bed type combustion furnace 1 is provided with a rice hull feeder 2 and a burner 3 on the side wall, a dispersion plate 4 and an air chamber 5 in the lower part, and a safety valve 6 in the upper part. , an exhaust port 7 is provided.

When burning rice husk, combustion air is sent from the blower 8 to the air chamber 5 and then passed through the distribution plate 4 to the furnace 1.
The silica sand 9 filled in an appropriate amount in the furnace 1 is fluidized, and the fuel in the fuel tank 10 is sent as a combustion gas from the burner 3 via the pump 11 and the solenoid valve 12, which is the ignition temperature of rice husks at 450°C. Heat the entire furnace to above ℃. Then, the rice husks are continuously fed into the furnace by the rice husks feeder 2 and burned.

The incinerated ash is carried along with the exhaust gas from the exhaust port 7 to the heat exchanger 13, where the fresh air from the blower 14 is warmed and turned into hot air, and then carried to the exhaust gas cyclone 15. The exhaust gas is separated into ash and gas in the exhaust gas cyclone 15, and the ash is taken out from the lower part, and the gas is discharged to the outside air from the chimney 18 via the adjustment damper 16 and the blower 17. Then, the hot air obtained from the heat exchanger 13 is passed through the air volume adjustment damper 19 to the kneading dryer 20.
heat source.

This rice husk incineration device can completely burn rice husks in a short period of time, requires less manpower, does not cause secondary pollution, and can effectively utilize waste heat, so it has attracted attention and is being used at rice centers and country elevators. ing. In this fluidized incinerator, the amount of air flowing in from the lower part of the dispersion plate 4 must be sufficient to appropriately fluidize the silica sand and burn the rice husks. If the amount of inflowing air is small, not only will the flow of silica sand be poor, but the calorific value of rice husks will also increase.
Since the temperature is as high as 3600 Kcal/Kg, the temperature inside the furnace becomes high especially from the upper part of the furnace to the area around the discharge port 7, which accelerates damage to the furnace wall. Furthermore, when the amount of incoming air is large, the temperature inside the furnace becomes low, but the amount of silica sand 9 scattered from the discharge port 7 together with the ash increases.

To explain this with Figure 2, if we take the temperature inside the furnace on the vertical axis and the wind speed inside the furnace (superficial velocity) on the horizontal axis, in the case of rice husk incineration, the most stable wind speed inside the furnace is about 0.8 to 1.2 m/S. However, at this time, the temperature in the upper part of the furnace becomes as high as 1300°C to 1600°C, which is not preferable. Therefore, in practice, the wind speed inside the furnace should be set at 1.5 to 1.8 m/cm, at which the temperature at the upper part of the furnace is below 1000℃.
It is used in S. This value is close to the sky velocity (referred to as terminal velocity, which is approximately 2.0 m/S for silica sand No. 5) at which the silica sand flies out of the discharge port 7 without falling, so a large amount of silica sand 9 is scattered. This scattered silica sand not only accumulates in the lower part of the heat exchanger 13, but also mixes into the ash separated by the exhaust gas cyclone 15. For this reason, it was necessary to select a superficial velocity that would form a stable fluidized bed, and to limit the amount of rice husk supplied so that the temperature at the upper part of the furnace did not exceed 1000°C.

The present invention was devised in view of the above points, and is a rice husk incineration device that can incinerate a large amount of rice husks at a temperature of 1000°C or less at the upper part of the furnace while forming a stable fluidized bed with little scattering of silica sand. The purpose of this is to increase the amount of air blown from the bottom of the dispersion plate to a superficial velocity of 1.5 to 1.8 m/s.
In order to reduce the temperature inside the furnace, secondary air is supplied from the upper side wall of the furnace body, and this secondary air contains scattered silica sand recovered by a heat exchanger. It is something.

Embodiments of the present invention will be described below with reference to FIGS. 3 and 4. Note that numbers 1 to 20 are the same as in the case of FIG.

A secondary air intake 21 is provided in the upper part of the side wall of the furnace 1 and is connected to a blower 22 by a pipe 23.

Further, a screw conveyor 24 is provided at the bottom of the heat exchanger 13 to take out the scattered silica sand 9.
The lower discharge port 25 of the heat exchanger 13 is connected to a fixed quantity feeder 26
It is connected to the piping 23 via. Note that the amount of secondary air can be adjusted by an adjustment damper 27 provided in the piping 23.

Next, the operation of the rice husk incineration apparatus configured as described above will be explained. First, combustion air is sent using a blower 8 so that the air velocity in the furnace is 0.8 to 1.2 m/s to form an optimal fluidized bed. Then, combustion gas is sent from the burner 3 to raise the temperature inside the furnace to 450°C or higher, and the rice husks are supplied.

As the rice husks burn, the temperature inside the furnace becomes higher and higher, and when it exceeds 1000°C, the blower 22 is activated to blow fresh air through the secondary air intake port 21. In this case, in order to enhance the cooling effect of the furnace 1, it is preferable to blow it along the inner wall of the furnace. The temperature inside the furnace changes depending on the supply state of rice husk and the combustion state, but a constant amount of secondary air is always fed to control the temperature inside the furnace (900 to 1000
℃) is performed by controlling the air volume of the primary air (the air volume of the blower 8). The combusted ash and exhaust gas are transported from the exhaust port 7 to the heat exchanger 13, where the fresh air from the blower 14 is warmed and turned into hot air, and the ash and combustion gas are transported to the exhaust gas cyclone 15. The exhaust gas cyclone 15 separates ash and gas, the ash is taken out from the bottom, and the gas is discharged to the outside air through the chimney 18.

Here, the ash flowing out from the discharge port 7 contains a small amount of small-diameter silica sand because the empty loading speed in the upper part of the furnace increases due to secondary air, and this silica sand is deposited below the heat exchanger 13. . Then, this silica sand is transferred to the discharge port 25 by the screw conveyor 24, flows into the secondary air blowing pipe 23 in fixed quantities by the quantitative feeder 26, and flows into the furnace together with the secondary air from the secondary air intake port 21. sent into 1.

As explained above, the rice husk combustion device according to the present invention reduces the amount of air blown from the bottom of the furnace body to the superficial velocity.
Optimal for sand bed fluidized bed of 0.8 to 1.2m/S,
Since secondary air is supplied from the upper part of the furnace side wall together with the silica sand recovered by a heat exchanger, a larger amount of rice husks than before can be optimally combusted at a furnace temperature of 1000°C or less. In addition, there is little silica sand scattered from the furnace, and the scattered silica sand is recovered from the heat exchanger into the furnace, so there is almost no need to replenish silica sand. Additionally, experiments have shown that the amount of air supplied into the furnace, including the amount of secondary air, can be reduced by more than 10% compared to the conventional method, resulting in energy savings. Furthermore, even when ash is recovered using an ash gas cyclone, ash of good purity can be obtained since there is no silica sand mixed in, and this has great practical effects, such as being able to utilize it effectively.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional rice husk incinerator using a fluidized bed incinerator, Figure 2 is a diagram showing the relationship between superficial velocity and furnace temperature in the equipment shown in Figure 1, and Figure 3 is a diagram of the present invention. FIG. 4 is a system diagram of a rice husk incinerator using the fluidized bed incinerator according to the invention, and FIG. 4 is a diagram showing the relationship between superficial velocity and furnace temperature of the device shown in FIG. 3. 1 is a combustion furnace, 2 is a rice husk feeder, 3 is a burner, 4 is a distribution plate, 5 is an air chamber, 7 is an exhaust port, 8 is a blower, 9 is silica sand, 13 is a heat exchanger, 14 is a blower, 15 is an exhaust gas cyclone, 21 is a secondary air intake port, 22 is a blower, 23 is piping, 24 is a screw conveyor, 25 is an outlet, 26 is a quantitative feeder,
27 is an adjustment damper.

Claims (1)

[Scope of utility model registration request] The incinerated rice is placed in a fluidized bed furnace, which has a supply port for rice husks on the side of the furnace body, and incinerates the rice husks by fluidizing the silica sand filled on the lower dispersion plate with combustion air sent from below the furnace body. In a rice husk incinerator that sequentially communicates a heat exchanger for obtaining a heat source for rice kneading and drying using rice husk ash and exhaust gas, and a cyclone for collecting incinerated ash, the above method is used to lower the temperature in the upper part of the furnace. A secondary air supply port is provided at the upper part of the side wall of the fluidized bed furnace and communicates with the blower through piping, and the silica sand discharge port at the bottom of the heat exchanger is connected to the piping to the secondary air supply port, and the fluidized bed furnace is connected to the secondary air supply port. A rice husk incinerator using a fluidized bed incinerator, characterized in that scattered and accumulated silica sand is returned to the incinerator using secondary air.